linux-kernel - Re: [PATCH V3 2/2] riscv: Use use_asid

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Message-ID: <CAJF2gTSa3LJKTRBv6NOvg0HtoKPL-5YyP6wY2=AJhQtAZwBBzg@mail.gmail.com>
Date:   Wed, 26 May 2021 11:12:40 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Christoph Hellwig <hch@....de>
Cc:     Anup Patel <anup.patel@....com>,
        Palmer Dabbelt <palmerdabbelt@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        linux-riscv <linux-riscv@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-arch <linux-arch@...r.kernel.org>,
        linux-sunxi@...ts.linux.dev, Guo Ren <guoren@...ux.alibaba.com>
Subject: Re: [PATCH V3 2/2] riscv: Use use_asid_allocator flush TLB

On Tue, May 25, 2021 at 8:35 PM Christoph Hellwig <hch@....de> wrote:
>
> On Tue, May 25, 2021 at 12:24:07PM +0000, guoren@...nel.org wrote:
> > From: Guo Ren <guoren@...ux.alibaba.com>
> >
> > Use static_branch_unlikely(&use_asid_allocator) to keep the origin
> > tlb flush style, so it's no effect on the existing machine. Here
> > are the optimized functions:
> >  - flush_tlb_mm
> >  - flush_tlb_page
> >  - flush_tlb_range
> >
> > All above are based on the below new implement functions:
> >  - __sbi_tlb_flush_range_asid
> >  - local_flush_tlb_range_asid
>
>
> This mentiones what functions you're changing, but not what the
> substantial change is, and more importantly why you change it.
>
> > +static inline void local_flush_tlb_range_asid(unsigned long start, unsigned long size,
> > +                                           unsigned long asid)
>
> Crazy long line.  Should be:
>
> static inline void local_flush_tlb_range_asid(unsigned long start,
>                 unsigned long size, unsigned long asid)
>
> > +{
> > +     unsigned long tmp = start & PAGE_MASK;
> > +     unsigned long end = ALIGN(start + size, PAGE_SIZE);
> > +
> > +     if (size == -1) {
> > +             __asm__ __volatile__ ("sfence.vma x0, %0" : : "r" (asid) : "memory");
> > +             return;
>
> Please split the global (size == -1) case into separate helpers.
Do you mean:
        if (size == -1) {
                __asm__ __volatile__ ("sfence.vma x0, %0"
                                :
                                : "r" (asid)
                                : "memory");
        } else {
                for (tmp = start & PAGE_MASK; tmp < end; tmp += PAGE_SIZE) {
                        __asm__ __volatile__ ("sfence.vma %0, %1"
                                        :
                                        : "r" (tmp), "r" (asid)
                                        : "memory");
                        tmp += PAGE_SIZE;
                }
        }

>
> > +     while(tmp < end) {
>
> Missing whitespace befre the (.
>
> Also I think this would read nicer as:
>
>         for (tmp = start & PAGE_MASK; tmp < end; tmp += PAGE_SIZE)
>
> > +static void __sbi_tlb_flush_range_asid(struct cpumask *cmask, unsigned long start,
> > +                                    unsigned long size, unsigned long asid)
>
> Another overly long line.
>
> Also for all thee __sbi_* functions, why the __ prefix?
I just follow the previous coding convention by __sbi_tlb_flush_range.
If you don't like it, I think it should be another coding convention
patchset.
This patchset is only to add the functions of tlb_flush_with_asid.

>
> > +     if (cpumask_any_but(cmask, cpuid) >= nr_cpu_ids) {
> > +             local_flush_tlb_range_asid(start, size, asid);
> > +     } else {
> > +             riscv_cpuid_to_hartid_mask(cmask, &hmask);
> > +             sbi_remote_sfence_vma_asid(cpumask_bits(&hmask), start, size, asid);
>
> Another long line (and a few more later).



-- 
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/